The present invention relates to an optical fiber cable.
Optical fiber cables are used to transmit information including telephone signals, television signals, data signals, and for Internet communication. To preserve the integrity of the signal transported by optical fiber cables, certain design factors warrant consideration.
A typical high fiber count cable design includes an outer cable jacket, within which multiple loose tubes are arranged in layers around a central strength member. For example, a typical outer cable jacket may include eighteen loose tubes (one six tube layer and one twelve tube layer) to thirty six loose tubes (with an additional eighteen tube layer) therein. Within each loose tube, typically twelve optical fibers are loosely arranged. Loose tube optical fiber cables refer to an arrangement wherein multiple individual optical fibers inside the loose tubes are substantially un-connected to the tubes. Such an arrangement effectively bundles a large number of optical fibers into a relatively condensed outer jacket.
U.S. Pat. No. 7,382,955 relates to an optical fiber cable that has a plurality of loose tubes, each of which contain at least one optical fiber. The tubes are arranged in at least two layers, each of which are rotated in the same uni-helical direction, and where each of the at least two layers are arranged having substantially the same lay length. A jacket encases the loose tubes, such that a user, desiring access to any one of the optical fibers in one of the loose tubes, may open the jacket, untwist the at least two layers, access a desired loose tube and accompanying fiber contained therein and perform a desired splicing action.
U.S. Pat. No. 5,343,549 relates to an optical fiber cable comprising a central strength member covered by a flame resistant plastic material. Surrounding the central member is at least one layer of buffer tubes each containing a plurality of light waveguides and a filling compound. The cable outer jacket is made of a flame resistant plastic. The two layers of buffer tubes are stranded with reverse oscillating lay around coated central member.
U.S. Pat. No. 6,859,592 relates to a fiber optic cable, comprising: optical fibers disposed in buffer tubes, said buffer tubes defining at least two layers generally stranded about a center area of the cable; said buffer tube layers defining a relatively inner layer of buffer tubes being closer to said center area, and an outer layer of buffer tubes being relatively further from said center area, said inner and outer buffer tube layers each comprising a respective helix value, said respective helix values being substantially the same.
U.S. 2003/118,299 relates to optical fibers disposed in buffer tubes, said buffer tubes defining at least two layers generally stranded about a center area of the cable; said buffer tube layers defining a relatively inner layer of buffer tubes being closer to said center area, and an outer layer of buffer tubes being relatively further from said center area, said inner and outer buffer tube layers each comprising a respective helix value, said respective helix values being substantially the same. Water swellable tapes can be disposed adjacent the buffer tubes.
U.S. Pat. No. 5,930,431 relates to a fiber optic cable comprising: a cable core with at least one optical fiber; a layer of tape surrounding said cable core, said layer of tape comprising a seam; a seam guard placed adjacent said seam; a jacket surrounding said seam guard; said seam guard comprising a substrate operative to prevent cable zippering, and a waterblocker attached to said substrate, said waterblocker operative to inhibit the migration of moisture into said cable core, said seam guard being operative to perform dual functions of inhibiting both jacket zippering and the ingress of moisture into said cable core. The cable core includes a dielectric central member surrounded by a first set of buffer tubes which buffer tubes 23 are, in turn, surrounded by a water-blocking tape.
U.S. Pat. No. 6,236,789 relates to a cable including a central strength member, surrounded by a plastic insulation coating. Plastic buffer tubes, each of which loosely contains optical fibers, are stranded longitudinally along the length of the strength member. A flowable filling material, such as a water blocking compound, buffer tube filling material, oil or gel, fills the spaces within the buffer tubes which are not occupied by the fibers. One or more water swellable yarn is disposed longitudinally along the central strength member in the interstices between the stranded buffer tubes and the strength member. The buffer tubes are enclosed by an inner plastic jacket and electrical conductor units comprising electrical conductors in side-by-side relation are disposed around and along the longitudinal length of the inner plastic jacket and each of the conductors is surrounded by insulation, and the cable is provided with an outer sheath.